Gradall G-550C Operation And Maintenance Manual page 27

G-660C & G-880C GRADALL (Crawler)
Allowing pins and bushings to be run to destruction will
result in accelerated wear to all the track components.
The space resulting from internal pin and bushing wear
permits the bushings to cock relative to the pies,
allowing the track to wander from side to side. This
complicates the job of keeping the track in fine, which
increases the wear on track roller and carrier roller
flanges, link sides, idler flanges and guiding guards.
The increase in track pitch resulting from internal pin
and bushing wear also creases a pitch mismatch between
the track chain and sprocket. This causes accelerated
sprocket tooth wear and can result in the sprocket
jumping teeth under load.
Sealed Track constitutes an important step in the attack
on undercarriage wear. The two saucer-shaped discs,
which are installed in the link counterbore at the end of
the bushing, seal out the dirt which normally works in
between the brushing and the counterbore. This reduc-
tion in the volume of abrasive dirt, acting on the internal
bearing surfaces of pins and bushings, results in a
reduction in the internal pin and bushing wear. This, in
turn, reduces wear to the entire undercarriage.
As pins and bushings wear, the track becomes longer and
track adjustment is necessary. There are two types of
wear on pins and bushings - external and internal.
External wear takes place on the bushings in the area
contacted by the sprocket driving teeth, which is about
1/3 of the surface of the track bushing.
TRACK ROTATION
excessive wear causes
stretch between bushings;
bushings then rice up
on sprocket teeth
Internal wear occurs on the outside diameter of the pin,
the inside diameter of the bushing, and outside diameter
of the ends of the bushing where they fit into the track
link counterbores.
TURN PIN
AND BUSHING
180°
27
OPERATION & MAINTENANCE